Rhodobacter sphaeroides as a biotechnological tool for remediation of chromate-contaminated environments

Common procedures to remove metal ions from effluents are economically expensive and cause incomplete removal along with toxic sludge or waste by-production. In recent years efficient and environment friendly methods to reduce heavy metal content have been investigated in bioremediation. Chromium for example is a widespread environmental pollutant due to the extensive employment of its compounds in different industrial fields. Chromate is a highly soluble non-essential oxyanion, toxic, carcinogenic and mutagenic to all forms of life. A methodology to evaluate the chromate influence on the photosynthetic growth of the facultative anaerobic bacterium Rhodobacter sphaeroides strain R26.1 was developed. This bacterium shows a noteworthy resistance to the metal as indicated by the high EC50. Furthermore as the metal concentration grows, a longer lag-phase highlights a progressive increasing detoxification time. It is likely that a reduction process occurs and that cell growth starts upon complete chromate reduction. The employment of Rhodobacter sphaeroides in bioremediation to detoxify chromate polluted liquid wastes in large-scale systems is proposed.